Patent Document 1 discloses a substrate rotating and holding device for a substrate spin treating apparatus. The substrate rotating and holding device includes a turntable to be rotated by rotation means, and support means which horizontally positions a substrate held by the turntable so as to space the substrate a predetermined distance from a surface of the turntable. A vertically movable member having substantially the same size as the substrate is provided on the turntable. In a substrate treatment process during which the turntable is rotated, the vertically movable member is located at an upper position adjacent to the substrate. Thus, as stated in Patent Document 1, a distance between a lower surface of the substrate and an upper surface of the vertically movable member is reduced, whereby mist generated during the substrate treatment process is prevented from flowing below the lower surface of the substrate.
An arrangement shown in FIGS. 1 to 3 in Patent Document 1 is adapted to vertically move up and down the vertically movable member relative to the turntable by means of a push-up mechanism which operates in response to a centrifugal force generated by the rotation of the turntable. In an arrangement disclosed in FIGS. 7 and 8 of Patent Document 1, fins are provided in an outer peripheral portion of the vertically movable member and, when the vertically movable member is rotated by the rotation of the turntable, the fins depress ambient gas to generate a lift force to lift the vertically movable member.
With these arrangements, however, it is impossible to move the vertically movable member sufficiently close to the lower surface of the substrate, because the centrifugal force or the lift force cannot be sufficiently generated when the substrate is rotated at a lower rotation speed. As a result, the mist generated during the substrate treatment process is liable to adhere to the lower surface of the substrate. Where an upper surface of the substrate being rotated is scrubbed with a brush, for example, the rotation speed of the substrate is about 100 rpm, making it impossible to sufficiently provide the centrifugal force or the lift force. Therefore, mist of a treatment liquid is liable to intrude into a space defined between the lower surface of the substrate and the vertically movable member during the scrubbing of the upper surface of the substrate, thereby contaminating the lower surface of the substrate.
An arrangement disclosed in FIGS. 9 and 10 of Patent Document 1 is adapted to vertically move up and down the vertically movable member by a push-up mechanism utilizing an air cylinder. Further, an arrangement shown in FIGS. 11 and 12 of Patent Document 1 includes bellows fixed to the vertically movable member at one end thereof, and is adapted to vertically move up and down the vertically movable member by pressurizing and evacuating the inside of the bellows for expansion and contraction of the bellows.
However, these arrangements each have a complicated structure, because driving means for the vertical driving is incorporated in a rotation system including the turntable and the vertically movable member, and requires supply of a driving force. In addition, there is a need for supplying and sucking driving air to/from a non-rotation system, so that a slide portion kept in frictional contact with an air supply/suction passage is present between the non-rotation system and the rotation system. This may result in generation of particles, which may adversely influence the substrate treatment.